High Resolution Waveguide Terahertz Time-Domain Spectroscopy

Terahertz time-domain spectroscopy accesses the frequency range between 100 GHz and 5 THz by using the coherent generation and detection based on femtosecond laser sources. On the way to obtain fingerprint absorption spectra of molecular solids, terahertz waveguides have proven to be a valuable tool to extend the results to narrow and high resolution linewidths of crystalline solids. We will discuss the development, properties and applications of terahertz waveguide geometries for spectroscopic applications, in particular high-resolution measurements using parallel-plate waveguides.     

Channel Selection Algorithm Optimized for Improved Performance in Cognitive Radio Networks

Wireless Personal Communications - A major concern in the recent past was the traditional static spectrum allocation which gave rise to spectrum underutilization and scarcity in wireless networks....     

Modular and Versatile Spatial Functionalization of Tissue Engineering Scaffolds through Fiber‐Initiated Controlled Radical Polymerization

Native tissues are typically heterogeneous and hierarchically organized, and generating scaffolds that can mimic these properties is critical for tissue engineering applications. By uniquely combining controlled radical polymerization (CRP), end‐functionalization of polymers, and advanced electrospinning techniques, a modular and versatile approach is introduced to generate scaffolds with spatially organized functionality. Poly‐ε‐caprolactone is end functionalized with either a polymerization‐initiating group or a cell‐binding peptide motif cyclic Arg‐Gly‐Asp‐Ser (cRGDS), and are each sequentially electrospun to produce zonally discrete bilayers within a continuous fiber scaffold. The polymerization‐initiating group is then used to graft an antifouling polymer bottlebrush based on poly(ethylene glycol) from the fiber surface using CRP exclusively within one bilayer of the scaffold. The ability to include additional multifunctionality during CRP is showcased by integrating a biotinylated monomer unit into the polymerization step allowing postmodification of the scaffold with streptavidin‐coupled moieties. These combined processing techniques result in an effective bilayered and dual‐functionality scaffold with a cell‐adhesive surface and an opposing antifouling non‐cell‐adhesive surface in zonally specific regions across the thickness of the scaffold, demonstrated through fluorescent labelling and cell adhesion studies. This modular and versatile approach combines strategies to produce scaffolds with tailorable properties for many applications in tissue engineering and regenerative medicine.     

Polyacetylene content and UV-induced 6-methoxymellein accumulation in carrot cultivars

The antifungal polyacetylenes falcarindiol and falcarinol, the production potential of the phytoalexin 6-methoxymellein (6-MM), and the carbohydrate profiles of five carrot cultivars were studied in order to assess variability in their content of these compounds as well as to determine the existence of any interrelationship among them. The polyacetylene content was measured in the peel of carrot roots shortly after harvest; the accumulation of 6-MM was measured in carrot slices incubated at 1°C after exposure to ultraviolet light (UV-C); and the carbohydrate content (glucose, fructose, sucrose and total non-structural), determined on whole carrots. Significant differences among the cultivars were noted in the content of polyacetylenes and 6-MM accumulation as well as in the carbohydrate constituents. The variation among the cultivars for the polyacetylene content and that for the accumulation of 6-MM were found to be independent of each other. The results suggest that cultivars with higher levels of antifungal compounds could be bred in order to improve their resistance to diseases. The carbohydrate profiles of the cultivars did not affect their production of 6-MM. Furthermore, 6-MM accumulation–UV dose response was similar for all the cultivars. Thus, a single dose of UV could be used to induce 6-MM in several cultivars of carrot.     

Test of the deterministic conjecture for the instantaneous time phase fluctuations of an oscillator

The fluctuations observed by recording the picosecond pulses of a mode-locked laser with a synchroscan streak camera are due to the laser jitter and to the variations of the zero crossing of the synchronization. By means of a simple model, it is shown that the dispersions measured when the synchronization is generated from the mode-locker oscillator reflect the instantaneous time phase fluctuations of this oscillator. From the study of the experimental recordings with methods of time series analysis it results that the phase noise of the electronic oscillator is consistent with an underlying low-dimensional strange attractor.     

MLEK crystal growth of (100) indium phosphide

We have used a combined magnetic liquid encapsulated Kyropoulos/Czochralski (MLEK/ MLEC) technique to produce twin-free indium phosphide (InP) crystals. This technique has advantages over the standard LEC method used for commercial production of InP. By stabilizing convective flows with a magnetic field and controlling the angle between solid and liquid, one can grow large diameter twin-free (100) InP crystals; they are shaped with a flat top as is typical for Kyropoulos growth, and then pulled from the magnetically stabilized melt as in Czochralski growth. This shaping method has the benefit of maximizing the number of single crystal wafers which can be sliced from the boule. MLEK InP growth is distinguished from other methods such as LEC and MLEC with respect to solid-liquid interface shape, dislocation density, and impurity distribution. This process has demonstrated that twin-free InP (100) crystals can be consistently grown.     

Synergistic interaction of 2-amino 4-methyl benzothiazole (AMBT) and benzotriazole (BTZ) offers excellent protection to mild steel exposed in acid atmosphere at elevated temperatures: Electrochemical,computational and surface studies

The synergistic interactions and corrosion protection properties of 2-amino 4-methyl benzothiazole, (AMBT) and 1, 2, 3-benzotriazole (BTZ) have been studied for mild steel in HCl at elevated temperatures. The extent of synergistic interaction increases with temperature. The methods of study include the conventional weight loss studies, computational screening, surface characterization and electrochemical studies. Quantum chemical approach was used to calculate some electronic properties of the molecules and to ascertain the synergistic interaction, inhibitive effect and molecular structures. The corrosion inhibition efficiencies and the global chemical reactivity relate to parameters like total energy, E_HOMO, E_LUMO and gap energy (ΔE). Condensed atom Fukui functions also calculated using DFT at B3LYP/6-31G* level, and were found to be correlating with the experimental results.     

Device fabrication on epitaxial Si-Ge alloys

PMOS transistors, p-n junctions and diffused resistors have been fabricated in Si-Ge alloy having a range of Ge content from 0 to 38%. The p-n junctions showed lower forward voltage drops than one would expect from simple band-gap lowering information. A Ge build-up at the surface may be causing this. MOS transistors exhibited low mobilities in the range of 20–50 cm²/V-s. The mobility value was affected by the surface condition and smoother surface areas resulted in the higher values of mobility. Diffused resistors had very high resistor values compared to control samples fabricated on silicon. Contact resistance problems were suspected but not proved to be the cause.     

下一代手机设计的集成技术

为了满足对于高度集成的无线电半导体解决方案日益增长的需求，蜂窝电话的技术创新正在沿着两个不同的方向发展。其一是在芯片级和封装级的功能集成，其二是完整的半导体系统解决方案。后者将所有必须的芯片、模块和软件捆绑到一个全面的解决方案中，从而简化了设计步骤．加快了产品进入市场的时间。