Fast codeword search algorithm using wavelet transform and partialdistance search techniques

A new fast codeword search algorithm for vector quantisers is presented. This algorithm performs a fast search in the wavelet domain of codewords using the partial distance search technique. Simulation results show that the algorithm has only 2% of the arithmetic complexity of the exhaustive search method     

Transistor design and application considerations for >200-GHz SiGe HBTs

SiGe HBT transistors achieving over 200 GHz f/sub T/ and f/sub MAX/ are demonstrated in this paper. Techniques and trends in SiGe HBT design are discussed. Processing techniques available to silicon technologies are utilized to minimize parasitic resistances and capacitances and thereby establish raw speeds exceeding III-V devices despite the higher mobility in those materials. Higher current densities and greater avalanche currents, which are required for establishing such high performance, are discussed as they relate to device self-heating and reliability and the degradation of the devices. Simple circuit results are shown, demonstrating 4.2-ps ring-oscillator delays.     

Reflection and transmission characteristics of lossy periodiccomposite structures

A periodic surface integral formulation is proposed to analyze the reflection and transmission properties of a lossy periodic composite structure which has circular conducting fibers embedded in a dielectric matrix. This formulation is based on the equivalence principle which represents the unknown electric and magnetic currents over the material discontinuity interfaces, and uses the structure periodicity and Poisson summation formula to reduce the problem to a periodic cell. These surface integral equations are then solved numerically, using the method of moments with pulse bases and point matching. Only the transverse magnetic (TM) case is analyzed and the numerical results such as reflected, transmitted, and dissipated powers for a single-layer fiber-reinforced composite structure are presented, in detail, to discuss the effects of frequency, incident angle, fiber radius, fiber conductivity, embedding dielectric, etc. A convergence study and a comparison with the previous published results are also included to confirm the accuracy of the new formulation     

Construction of spiro-oxaquinolizidinone framework of Upenamide via organoiron complexes

An organoiron approach toward the synthesis of an elaborated tricyclic spiro-oxaquinolizidinone ring has been accomplished. The key intermediate was efficiently prepared through a nitrile addition to the appropriately functionalized cyclohexadienylium-Fe(CO)₃ perchlorate salt to install the requisite quaternary center in the spiro-oxaquinolizidinone ring.     

A solution study on the local and global structure changes of cytochrome c: an unfolding process induced by urea

The local and global structural changes of cytochrome c induced by urea in aqueous solution have been studied using X-ray absorption spectroscopy (XAS) and small-angle X-ray scattering (SAXS). According to the XAS result, both the native (folded) protein and the unfolded protein exhibit the same preedge features taken at Fe K-edge, indicating that the Fe(III) in the heme group of the protein maintains a six-coordinated local structure in both the folded and unfolded states. Furthermore, the discernible differences in the X-ray absorption near-edge structure (XANES) of these two states are attributed to a possible spin transition of the Fe(III) from a low-spin state to a high-spin state during the unfolding process. The perseverance of six-coordination and the spin transition of the iron are reconciled by a proposed ligand exchange, with urea and water molecules replacing the methionine-80 and histidine-18 axial ligands, respectively. The SAXS result reveals a significant morphology change of cytochrome c from a globular shape of a radius of gyration R(g) = 12.8 A of the native protein to an elongated ellipsoid shape of R(g) = 29.7 A for the unfolded protein in the presence of concentrated urea. The extended X-ray absorption fine structure (EXAFS) data unveil the coordination geometries of Fe(III) in both the folded and unfolded state of cytochrome c. An initial spin transition of Fe(III) followed by an axial ligand exchange, accompanied by the change in the global envelope, is proposed for what happened in the protein unfolding process of cytochrome c.     

Using high-concentration trypsin-immobilized magnetic nanoparticles for rapid in situ protein digestion at elevated temperature

We describe an innovative approach - using a high concentration of trypsin-modified magnetic nanoparticles (TMNPs) - for the rapid and efficient digestion of proteins at elevated temperature. The required digestion time could be reduced to less than 10 s. After digestion, the TMNPs were collected magnetically from the sample solution for reuse and the digested peptides were characterized using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. Protein digestion was optimized when using the TMNPs (5 microg/microL) at 57 degrees C; a significantly high peptide coverage was achieved for protein identification (e.g., 98% for lysozyme). Although a high concentration of TMNPs was used for digestion, the short digestion time led to much lower amounts of trypsin peptides being produced through self-digestion. As a result, interference in the mass spectrometric detection of the peptide ions was reduced significantly.     

High Quality Carbon Nanotubes on Conductive Substrates Grown at Low Temperatures

For carbon nanotubes (CNTs) to be exploited in electronic applications, the growth of high quality material on conductive substrates at low temperatures (<450 °C) is required. CNT quality is known to be strongly degraded when growth is conducted on metallic surfaces, particularly at low temperatures using conventional chemical vapor deposition (CVD). Here, the production of high quality vertically‐aligned CNTs at low substrate temperatures (350–440 °C) on conductive TiN thin film using photo‐thermal CVD is demonstrated by confining the energy required for growth to just the catalyst using an array of optical lamps and by optimizing the thickness of the TiN under‐layer. The thickness of the TiN plays a crucial role in determining various properties including diameter, material quality, number of shells, and metallicity. The highest structural quality with a visible Raman D‐ to G‐band intensity ratio as low as 0.13 is achieved for 100 nm TiN thickness grown at 420 °C; a record low value for low temperature CVD grown CNTs. Electrical measurements of high density CNT arrays show the resistivity to be 1.25 × 10^‐2 Ω cm representing some of the lowest values reported. Finally, broader aspects of using this approach as a scalable technology for carbon nanomaterial production are also discussed.     

Diffusion slowdown in the nanostructured liquid Ga‐Sn alloy

The diffusion of gallium in liquid Ga‐Sn alloy embedded into different porous silica matrices was studied by NMR. Spin relaxation was measured for two gallium isotopes, ⁷¹Ga and ⁶⁹Ga, at two magnetic fields. Pronounced rise of quadrupole contribution to relaxation was observed for the nanostructured alloy which increased with decreasing the pore size. The correlation time of atomic mobility was evaluated and found to be much larger than in the relevant bulk melt which evidenced a pronounced diffusion slowdown in the Ga‐Sn alloy under nanoconfinement. It is shown that the diffusion was slower by a factor of 30 for the alloy within 7 nm pores. The spectral densities of electric field gradients at zero frequency were found to double for the finest pores. The Knight shift was found to decrease but slightly for the nanostructured alloy.     

Application of Two Hopfield Neural Networks for Automatic Four-Element LED Inspection

A system for the automatic inspection of LED wafer defects is proposed to detect defective dies in a four-element (aluminum gallium indium phosphide, AlGaInP) wafer. There are over 80000 dies on an LED wafer. Defective dies are typically visually identified with the aid of a scanning electron microscope. This process involves dozens of operators or engineers visually checking the wafers and hand marking the defective dies. However, wafers may not be fully and thoughtfully checked, and different observers usually find different results. These shortcomings lead to significant labor and production costs. Therefore, a solution that consists of two Hopfield neural networks, of which one is used to identify the LED die regions and the other is used to cluster the die into three groups, is proposed to facilitate the detection of defective dies in wafer images. The experimental results show that the proposed method successfully detects defective dies in a four-element wafer.